e cloud simulations C Octavio Domnguez Giovanni Rumolo

e cloud simulations C. Octavio Domínguez, Giovanni Rumolo, Frank Zimmermann Thanks to Humberto Maury Cuna 26 th November 2010 - e - cloud simulations

Contents 1) SPS benchmarking : - SEY scan for different bunch spacing and reflection coefficient - Vacuum pipe shape study - Emittance scan 2) Plans Discussion: - Further cross check with Humberto - Plan for LSS 3 simulation; Memory effect - Plan for coupled-bunch wake field 26 th November 2010 - e - cloud simulations 2

1) SPS benchmarking 26 th November 2010 - e - cloud simulations 3

SPS - Introduction - Goal: To find onset multipacting SEY for several input parameters 26 th November 2010 - e - cloud simulations 4

SPS - Introduction -The standard parameters: • Bunch spacing = 50 ns • Energy = 450 Ge. V (SPS extraction) • R = 0. 7 • Shape: Elliptical approach of the electron cloud monitor at SPS: 24. 3 mm • emax = 230 e. V 70. 0 mm • Gas pressure = 9 n. Torr • Beam size: The one at the electron cloud monitor at SPS (e. Nx, Ny = 3. 0 mm) - sx = 0. 9 mm - sy = 0. 4 mm - sz = 11. 8 cm • Nb = 1. 1 · 1011 ppb 26 th November 2010 - e - cloud simulations 5

SPS – SEY scan sx= 0. 9 mm; emax= 230 e. V; sy= 0. 4 mm; Nb=1. 1 1011 ppb; sz= 11. 8 cm; P = 9 n. Torr; Bs [ns] R onset 25 0. 5 1. 4 50 0. 5 1. 8 75 0. 5 2. 3 25 1. 0 1. 3 50 1. 6 75 1. 0 1. 9 24. 3 mm e- cloud monitor (elliptical approach) 70. 0 mm 26 th November 2010 - e - cloud simulations 6

SPS – SEY scan 26 th November 2010 - e - cloud simulations 7

1. 2) Vacuum pipe shape 26 th November 2010 - e - cloud simulations 8

SPS – Pipe shape 24. 3 mm 70. 0 mm 47. 15 mm 70. 0 mm 26 th November 2010 - e - cloud simulations 24. 3 mm 47. 15 mm 9

SPS – Pipe shape sz= 11. 8 cm; Nb=1. 1 1011 ppb; emax= 230 e. V; R = 0. 7; bs = 50 ns; P = 9 n. Torr; Pipe shape sx[mm] sy[mm] sx[m] sy, sz [m] onset e- cloud monitor (Elliptical) Elliptical 0. 9 0. 4 0. 07 0. 0243 1. 7 0. 9 0. 4 0. 07 0. 04715 1. 3 Round 0. 9 0. 4 0. 07 1. 5 Elliptical 0. 9 0. 4 0. 04715 0. 0243 1. 7 Round 0. 9 0. 4 0. 0243 1. 6 MBA (Elliptical) MBB (Elliptical) LHC type (Elliptical) 0. 89947 0. 756129 1. 0 0. 460687 0. 670483 1. 0 0. 078 0. 066 0. 022 0. 01925 0. 2575 0. 018 2. 0? <1. 7 X 26 th November 2010 - e - cloud simulations 10

1. 3) Emittance scan 26 th November 2010 - e - cloud simulations 11

SPS – e scan emax= 230 e. V; bs = 50 ns; R = 0. 7; Nb=1. 1 1011 ppb; P = 9 n. Torr; e. Nx, Ny [mm] sx [mm] sy [mm] onset 1. 5 0. 78912 029059 1. 7? 2. 5 0. 893224 0. 37515 1. 7 3. 0 0. 940968 0. 410956 1. 7 3. 5 0. 986403 0. 443883 1. 7 4. 5 1. 07151 0. 503317 1. 7? 5. 5 1. 15033 0. 556437 1. 7? 24. 3 mm e- cloud monitor (elliptical approach) 70. 0 mm 26 th November 2010 - e - cloud simulations 12

SPS benchmarking – conclusions Ø e- cloud simulation for SPS bending magnets are being redone exploring different parameters Ø Agreement (apparently) with previous simulations carried out by Giovanni Ø Round shape option Worse results Ø Emittance scan for different LHC type of beams Very small differences (negligible) Ø To do: • Drifts • Quadrupoles • Modify code to simulate an elliptic/rectangular shape for a better approach (already succeeded once by D. Schulte) Ø Questions for discussion: • emax dependence of SEY • b functions at the e- cloud monitor, i. e. beam size • Differences between SPS and LHC simulations 26 th November 2010 - e - cloud simulations 13

2) Plans 26 th November 2010 - e - cloud simulations 14

2. 1) Further cross check with Humberto 26 th November 2010 - e - cloud simulations 15

2. 2) LSS 3 simulation; Memory effect 26 th November 2010 - e - cloud simulations 16

LSS 3 - Motivation Ø The biggest problems for e- cloud were found in the LSS 3 section Ø That makes interesting to explore it in more detailed 26 th November 2010 - e - cloud simulations 17

Vincent Baglin 26 th November 2010 - e - cloud simulations 18

2. 3) Coupled-bunch wake field 26 th November 2010 - e - cloud simulations 19